The frequency band between 5010MHz and 5030MHz offering a bandwidth of 20MHz was already allocated as C band portion for Radio Navigation Satellite Service (RNSS) applications in the course of the World Radio Conference 2000 (WRC-2000). In the future Global Navigation Satellite Systems (GNSS) receiver design, the use of pilot channel in quadrature with the data channel will provide potential advantages to users in signal processing of a receiver. Increasing signal power on the pilot channel at the expense of lower power on the data channel is good for available C/N_0 region that is better tracking performance but not for data bit demodulation. The higher the bit rate, the higher the Bit-Error-Rate (BER) and the worse tracking loop stability. And so a trade-off between navigation data bit rate and pilot channel signal power in terms of the available carrier-to-noise ratio as an important factor affecting the overall system performance must be analyzed in detail. The measurement errors and tracking thresholds are closely related, and when the measurement errors exceed a certain boundary, the receiver loses lock that is to say it doesn't track stably. Also, in order to define a realistic value for tracking thresholds at a receiver side, all error sources such as thermal noise phase jitter, dynamic stress error, oscillator's Allan deviation phase noise jitter, vibration induceed phase noise jitter in the Phase Lock Loop (PLL) of a standard receiver are taken into account in the study. Therefore, based on the results of signal tracking loop stability and BER analyses, the required minimal 0 C / N on the optimization of the pilot-only tracking, data-only tracking, or combined tracking, the bit rate, and the signal power split between data and pilot channels can be obtained. And then the required transmit signal power level based on optimum data rate and signal power split at satellites for C band with considering link budget can be efficiently calculated.

Keywords: C band, optimum data rate and signal power split, required transmit signal power level, error sources, tracking thresholds